Constraining all axis movement from one object to a single axis on another.

Hope the title made sense. Basically what I want to achieve is having an object attached to the side of another that follows the rotations and stays attached, but also transfers it to rotating on a single axis. I’ve been toying with the ‘Transformation’ but can’t quite get what I’m looking for.

The setup is a simple four chain armature attached to four ‘arms’. That setup works fine, as well as the gear attached to the side of the base arm. That gear follows as it should but I can’t quite figure out how to rig the addition constrained motion.

You could try rigging the cog to a separate bone that is parented to the arm bone, and then rotate the bone.